PC12 is a secretory cell line that was cloned from transplantable pheochromocytoma (Greene and Tischer, 1976). In the presence of NGF, PC12 stops dividing, extends neurites, and develops cholinergic characteristics. I have demonstrated that low concentrations of adenosine (less than 100 to 500 micro M) are capable of causing neurite outgrowth and may inhibit cell division, neurite formation, enzyme induction, Ca ions uptake, cAMP metabolism and cell adhesiveness. I will then explore the relationship between NGF action; (2) if adenosine acts intracellularly or extracellularly. If adenosine acts extracellularly, I will study the nature of the adenosine receptor and ask if it might control cAMP levels or Ca ions flux. If adenosine acts within the cell, I will determine if it affects methylation or nucleotide metabolism. Mutants that fail to respond to NGF and adenosine will be isolated and used to study the mechanism by which PC12 cells respond to NGF and AR. Using these approaches, I hope to elucidate the nature of the steps modulated by NGF and adenosine that leads to effects on neurite extension, growth control, and induction of cholinergic characteristics.